This invention relates to a stroke control valve for a variable displacement reciprocating piston device, and in particular, a radial piston pump.
It is known that the displacement of a radial piston pump can be controlled by controlling the fluid pressure in its interior or stroke control chamber. This concept is illustrated in U.S. Pat. No. 3,002,462 to Raymond. One prior art method of accomplishing this has been to meter high pressure pump output pressure back to the stroke control chamber to reduce the pump output when the output pressure is too high. However, energy usage can be reduced by flowing low pressure oil to the stroke control chamber during standby conditions instead of continuously communicating high pressure fluid to it. A valve which performs this function is described in U.S. Pat. No. 3,526,468 issued to Moon et al, and assigned to the assignee of the present invention. However, the valve of U.S. Pat. No. 3,526,468 also permits high pressure oil to flow into the charge pump circuit, thus reducing the rapidity of pump de-stroking.